Green Manuring. 



7 



This table shows that the crop of peas ploughed in was 

 equal in manurial value to more than half a ton of nitrate 

 of soda per acre, and was in this respect much superior 

 to all the other crops. Blue lupins gave the next best 

 return, as represented by an equivalent of value in nitrate 

 of soda ; but it must be noted that in the case of the peas 

 the amount of dry substance required to yield the equiva- 

 lent of 1,267 lbs. of nitrate of soda, or 7,140 lbs., was pro- 

 portionately less than in the blue lupins, whose equivalent 

 value in the form of nitrate of soda was 1,081 lbs., from 

 7,020 lbs. of dry substance. M. Grandeau states that 

 another great advantage of this system of green manuring 

 is that the nitrogen supply is gradually evolved as the 

 buried substance decays, and is therefore available for the 

 use of the crop throughout its growth. 



Allusion has been made to the mechanical action upon the 

 soil of the roots of leguminous plants, which, as M. 

 Grandeau puts it, exercise a considerable influence upon the 

 fertility of land. This was not realised in any way until 

 the important experiments at Lupitz had proved It m a 

 striking manner. From these experiments it appears that 

 when rye succeeded a crop of lupins its roots penetrated 

 over three feet into the earth, and the roots of potatoes 

 descended still deeper ; but upon land adjoining, manured 

 with farmyard manure, and not having had a previous crop 

 of lupins, the roots of rye descended only between 16 and 

 24 inches. 



The results of experiments in this direction are graphi- 

 cally shown by the figure on the next page. 



This figure is reproduced from a photograph of deep 

 sections of two fields together 37 acres in extent, cultivated 

 for the potato crop wnth and without green manuring. 



The letters A, B, C, D denote the nature of the strata of 

 soil and subsoil of Field i through which the roots of the 

 lupins of the previous crop had made channels, and facilitated 

 the passage of the roots of the potato plants. Following 

 these channels, the roots of the potato plants got into D, 

 which on account of its depth had retained moisture. Thi^ 

 caused them to spread laterally in an extraordinary manner,. 



